Automakers are increasingly relying on the mixed use of chemical and natural fibers in automobiles. In addition to the sustainability aspect and the use of renewable resources associated therewith, manufacturers may seek to save weight by using alternative materials and material combinations.
In addition, natural fibers such as sisal, coconut or hemp are no longer used only in non-visible functional components automobiles, and may also be used in a visible area, such as in the vehicle interior. The requirements of these materials are often very high. Even under constantly changing temperature and moisture conditions, microorganisms should not be allowed to settle. When microorganisms are allowed to settle, undesirable visual effects, such as mildew stains, may occur. Further, unpleasant odors may be generated in the vehicle interior. While resistance to such undesirable visual effects and odors must be ensured over the life of the vehicle, the focus after decommissioning of the vehicle, in contrast, is placed on swift and substantially residue-free decomposition of the interior fittings and attachment parts in the spirit of protecting the environment.
Natural fibers and wood may be quickly subject to the growth of mold due to moisture and heat, which is undesirable for the surface appearance and for health reasons. The risk of mold growth may be high in parts made of compressed natural fiber-reinforced polymer composites.
A large variety of corresponding fungicides exist; however they may be applied and used only conditionally, based on the Ordinance on Hazardous Substances, and additionally may change the mechanical and visual properties of the parts produced therefrom, which are used in the automobile interior.
The group of organic active fungicidal agents has a heterogeneous composition and can be difficult to manage. For example, thiabendazole, an active agent from the group of benzimidazoles, may be used as a systemic fungicide having protective and curative activity for natural fibers. While the toxicity of thiabendazole is low according to the German Federal Institute for Health Protection and Veterinary Medicine, the substance was found to have a carcinogenic effect in animal experiments.